Recognition of ST Elevation by Paramedics M Whitbread, V Leah, T Bell, T J Coats

PREHOSPITAL CARE Emerg Med J: first published as 10.1136/emj.19.1.66 on 1 January 2002. Downloaded from Recognition of ST elevation by paramedics M Whitbread, V Leah, T Bell, T J Coats ......

Emerg Med J 2002;19:66–67

See end of article for Objective: To define the ability of UK paramedics to recognise ST segment elevation using a prehos- authors’ affiliations pital 12 lead electrocardiogram (ECG)...... Methods: Analysis of the diagnostic ability of seven paramedics 12 months after a two day training Correspondence to: course, using interpretation of a 12 lead ECG by two cardiologists as the criterion standard. Compari- MrTJCoats,Accident and son of paramedic and A&E SHO diagnosis to determine accuracy, specificity, sensitivity, negative pre- Emergency Department, dictive value, and positive predictive value of paramedic interpretation. Royal London Hospital, Whitechapel, London Results: Paramedics showed a median accuracy of 0.95 (95% CI 0.88 to 0.98), a specificity of 0.91 E1 1BB, UK; (95% CI 0.53 to 1.0), a sensitivity of 0.97 (95% CI 0.94 to 0.99), a NPV of 0.77 (95% CI 0.62 to [email protected] 0.92) and a PPV of 0.99 (95% CI 0.92 to 1.0). This was not significantly different from a group of Accepted for publication experienced A&E SHOs. 11 May 2001 Conclusions: UK paramedics can recognise ST elevation using a 12 lead ECG. Radio transmission of ...... an ECG may not be necessary to pre-alert the hospital.

arly diagnosis of acute myocardial infarction (AMI) is a priority during the in hospital management of the patient Table 1 Overall performance (95% confidence Ewith chest pain, to enable early thrombolysis.1 A logical intervals) for paramedics and SHOs extension of early diagnosis is prehospital recognition of the Paramedic A&E SHO ECG criteria for thrombolysis by ambulance service paramedics. There are two methods of recognising ECG criteria for Sensitivity 0.97 (0.94 to 0.99) 0.97 (0.96 to 0.99) Specificity 0.91 (0.53 to 1.0) 0.67 (0.58 to 0.73) thrombolysis before the patient arrives at the hospital. Either Accuracy 0.95 (0.88 to 0.98) 0.93 (0.90 to 0.94) the 12 lead electrocardiogram (ECG) is transmitted to a doctor Negative predictive value 0.77 (0.62 to 0.92) 0.85 (0.77 to 0.92) who makes a diagnosis (and may communicate this diagnosis Positive predictive value 0.99 (0.92 to 1.0) 0.93 (0.91 to 0.95) back to the ambulance crew), or alternatively ambulance paramedics are trained to interpret the 12 lead ECG.

Transmission of an ECG requires technology at both ends of http://emj.bmj.com/ the transmission, a fault free line, the immediate availability of a senior doctor to make the diagnosis, and a system for also classified in the same way by a group of A&E SHOs communicating the diagnosis back to the ambulance crew. towards the end of a six month A&E post. To provide a This system has a one in five chance of problems with criterion (gold) standard each ECG was also classified by two communication, may result in delay and requires expensive consultant cardiologists, with an emergency physician provid- technology.2 These problems are avoided if the paramedic can ing a third opinion where there was disagreement. recognise ST segment elevation. The ability of UK paramedics The medians with 95% confidence intervals were calculated to interpret the 12 lead ECG, and the training required to for sensitivity, specificity, accuracy, negative predictive value on September 25, 2021 by guest. Protected copyright. acquire and maintain this skill has not been established. (NPV) and positive predictive value (PPV) of paramedic and This study was designed to test the recognition of ST eleva- SHO classifications. tion by paramedics 12 months after a short training course in the interpretation of the 12 lead ECG. RESULTS Of the 10 paramedics initially trained seven remained at the METHODS same ambulance station after a year and were tested. The sen- A group of 10 London Ambulance Service paramedics were sitivity, specificity, accuracy, NPV and PPV of classification of trained over two days, learning how to record a 12 lead ECG, ECGs by paramedics and SHOs are shown in table 1. how to recognise ST elevation (and bundle branch block) and how to communicate their diagnosis to the receiving accident and emergency (A&E) department. The paramedics were DISCUSSION taught to recognise a normal ECG, anterior myocardial infarc- Prehospital recognition of patients who may benefit from tion, inferior myocardial infarction, and left bundle branch thrombolysis is not an established part of prehospital care in block (QRS complex > 0.1s with no “R” wave in V1 and no the UK. The role of prehospital diagnosis (if any) has yet to be “Q” wave in V6). The criteria for of patients potentially requir- defined. There are two questions that need to be answered: (1) ing thrombolysis were ST elevation of 2 mm or more in two Is prehospital recognition practical? (2) Is prehospital consecutive precordial leads, or 1 mm or more in two consecu- recognition worthwhile? tive limb leads, or new left bundle branch block. Paramedics were tested 12 months later, after taking part in a study of the effect of prehospital diagnosis on door to needle ...... time. Each paramedic was given 100 minutes to classify Abbreviations: AMI, acute myocardial infarction; ECG, whether significant ST elevation (as defined above) was electrocardiogram; PPV, positive predictive value; NPV, negative present on 100 prehospital 12 lead ECGs. The same ECGs were predictive value

www.emjonline.com Recognition of ST elevation by paramedics 67

The transmission of a prehospital diagnosis before the treatment. This study has shown that prehospital identifica- Emerg Med J: first published as 10.1136/emj.19.1.66 on 1 January 2002. Downloaded from arrival of the patient enables the hospital to “gear up” to pro- tion of ST elevation by paramedics is possible in the UK. The vide a swift response once the patient arrives. Several studies effect of the introduction of this technique now requires have shown that this decreases the door to needle time.3–6 A assessment. prehospital diagnosis is also required if prehospital throm- This study has shown that prehospital recognition of ECG bolysis is contemplated.7 These studies have shown that criteria for thrombolysis by paramedics is practical. UK para- prehospital recognition of patients who may benefit from medics can recognise significant ST elevation in a prehospital thrombolysis is worthwhile in the American systems exam- ECG with a sensitivity of 97% and a specificity of 91%. This ined. A similar benefit could be expected in Britain. information contributes to the analysis of the role of prehos- There are many differences in training between British and pital diagnosis in the treatment of patient with AMI. Only American paramedics. This study shows that British paramed- relatively small changes in ambulance training and equipment ics, after a short training course, are able to recognise signifi- would be required to enable routine prehospital identification cant ST elevation on a 12 lead ECG. This study was performed of patients with chest pain and significant ST changes. using a group of well motivated and enthusiastic paramedics from a single ambulance station with a close connection to a teaching hospital. The same results might not be obtained if ACKNOWLEDGEMENTS We would like to thank Professor Douglas Chamberlain and Dr Peter all paramedics were trained in this skill. Mills for their assistance in providing our gold standard. This project Some skills are performed so infrequently by paramedics was supported by a grant from the medical audit department of the 8 that there are major concerns about skill retention. As Royal Hospitals NHS Trust. Equipment was loaned by Physio-Control patients with both non-cardiac chest pain and AMI are com- UK Ltd. This study would not have been possible without the enthu- mon, prehospital diagnosis is a skill that will be frequently siastic support of the London Ambulance Service Paramedics of Pop- practised. There is therefore likely to be good skill retention. As lar Ambulance Station. the ambulance service works closely with A&E staff, immediate feedback is available to paramedics, which may make Contributors: Mark Whitbread initiate the study, discussed core ideas, participate in protocol design, taught the paramedics, oversaw data re-training unnecessary. The need for re-training could be collection and assisted with writing of the paper. Vicki Leah discussed easily assessed using a similar method to that used in this core ideas, participate in protocol design, taught the paramedics, par- study. ticipated in data analysis and assisted with writing the paper. Tim Bell There is little difference between paramedics and SHOs in participated in data collection, assisted in data analysis and editing of this study apart from the trend towards lower specificity in the the paper. Tim Coats discussed core ideas, participate in protocol SHO group. Decision making is influenced by the perceived design, oversaw data analysis and wrote the paper. Tim Coats is the risks and benefits of different outcomes. A&E SHOs may be guarantor of the paper. rather afraid of missing an AMI and therefore be more suspi- cious of marginal ST changes, leading to a larger number of ...... false positives and a lower specificity. The doctors may also be Authors’ affiliations unconsciously answering the question “Does this patient have M Whitbread, Resuscitation Service, Royal Hospitals NHS Trust, London, UK an acute myocardial infarction?” rather than “Does this ECG V Leah, Resuscitation Service, Joyce Green Hospital, Dartford, UK show ST elevation?”, or using a different set of ST segment T Bell, T J Coats, Department of Accident and Emergency, St elevation criteria for the diagnosis of AMI.9 Bartholomew’s and the Royal London School of Medicine, Queen Mary These data are useful in planning a system for alerting the and Westfield College, London, UK http://emj.bmj.com/ hospital prior to arrival of a patient with AMI. Diagnosis by paramedic may remove both the need for transmission of REFERENCES ECGs and the requirement that a senior doctor is immediately 1 FibrinolyticTheapyTrialists’(FFT)CollaborativeGroup. Indications for available to interpret the transmitted document. This would fibrinolytic therapy in suspected acute myocardial infarction: reduce both the cost and the organisational change required collaborative overview of early mortality and major morbidity results from all randomised trials of more than 1000 patients. Lancet for prehospital diagnosis. The equipment change required is 1994;343:311–22. already occurring, with new cardiac monitors being able to 2 Aufderheide TP, Hendley GE, Woo J, et al. A prospective evaluation of on September 25, 2021 by guest. Protected copyright. record a 12 lead ECG. The training requirement would be a prehospital 12-lead ECG application in chest pain patients. J short course for all paramedics. No change would be required Electrocardiol 1992;24 (suppl):8–13. 3 Foster DB, Dufendach JH, Barkdoll CM, et al. Prehospital recognition of to the current system for transmitting messages from ambu- AMI using independent nurse/paramedic 12-lead evaluation: Impact on lance crews to the hospital. in-hospital time to thrombolysis in a rural community hospital. Am J Emerg These data are also useful in the debate about paramedic Med 1994;1:25–31. 4 Kennedy JW, Weaver WD. The potential for prehospital thrombolytic administration of prehospital thrombolysis, as the ability to therapy. Clin Cardiol 1990;13:23–6. recognise significant ECG changes has been defined. However, 5 Karagounis L, Ipsen SK, Jessop MR, et al . Impact of field-transmitted it is important to emphasise that this study did not examine electrocardiography on time to in-hospital thrombolytic therapy in acute myocardial infarction. Am J Cardiol 1990;66:786–91. the ability of a paramedic to diagnose AMI. Diagnosis of AMI 6 Gibler WB, Kereiakes DJ, Dean EN. Prehospital diagnosis and treatment is more complex than simply identifying ST elevation on a 12 of acute myocardial infarction: a North-South perspective. Am Heart J lead ECG. Much more work would have to be done before any 1991;121:1–11. 7 Weaver WD, Cerqueira M, Hallstrom AP. Prehospital-initiated vs statement could be made about the diagnostic abilities of a hospital-initiated thrombolytic therapy. The Myocardial Infarction Triage paramedic. In particular the probable number of diagnostic and Intervention Trial. JAMA 1993;270:1211–16. errors must be known before any risk/benefit calculation can 8 Latman LS , Wooley K. Knowledge and skill retention of emergency 10 care attendants, EMT-As and EMT-Ps. Ann Emerg Med 1980;9:183–9. be made about prehospital thrombolysis. 9 Otto LA, Aufderheide TP. Evaluation of ST segment elevation criteria for The effect of widespread introduction of prehospital recog- the prehospital electrocardiographic diagnosis of acute myocardial nition of ST elevation has not been established. It can be infarction. Ann Emerg Med 1994;23:17–24. argued that if there was an efficient in hospital response to 10 Aufderheide TP, Haselow WC, Hendley GE, et al. Feasibility of prehospital r-TPA therapy in chest pain patients. Ann Emerg Med every patient a prehospital diagnosis would be unnecessary, 1992;21:379–83. however many hospitals still give a less than ideal response to 11 Hood S, Birnie D, Swan L, et al. Questionnaire survey of thrombolytic these patients.11 12 No single intervention will universally pro- treatment in accident and emergency departments in the United Kingdom. BMJ 1998;316:274. vide early thrombolysis. All parts of the chain of care from ini- 12 Birkhead JS. Time delays in provision of thrombolytic treatment in six tial symptoms onwards should be optimised to provide early district hospitals. BMJ 1992;305:445–8.